Heterostructured AlCoCrFeNi2.1 high entropy alloy with simultaneously improved strength and ductility via laser powder bed fusion

Heterostructure has been evidenced to generate back stress-induced strengthening during deformation and can overcome the strength-ductility trade-off of the material. However, the advantage of additive manufacturing (AM) technology in freely tailoring local material properties has not been fully exploited in the preparation of heterostructured (HS) materials. In this work, we demonstrate changing the scanning mode of laser powder bed fusion (LPBF) to create heterogeneous regions, thereby successfully preparing AlCoCrFeNi_2.1 eutectic high entropy alloy (EHEA) with a layered heterostructure. The results show that by controlling the laser scanning mode, the phase distribution and grain size can be regulated, enabling the fabrication of soft and hard regions. The layered HS material, formed by combining the soft and hard regions, exhibits superior mechanical properties (the yield strength, ultimate tensile strength, and elongation are 1032 ± 22.6 MPa, 1310 ± 26.3 MPa, and 18.7 ± 0.8 %, respectively), representing improvements of 13.9 %, 5.9 %, and 8.7 % compared to the non-HS samples. The simultaneous enhancement in strength and ductility of this layered HS material is mainly due to the back stress-induced strengthening from the high-density interfaces of the heterogeneous regions during deformation. These results promote the development of high-performance materials with free-designed heterostructures fabricated by LPBF.